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poison hemlock(Conium maculatum)
ODA rating: B
 
USDA Symbol: COMA2
Oregon poison hemlock distribution
 
Click on image to view larger photo.
 
Images courtesy of Weed Science Society of America

 
Images courtesy of Weed Science Society of America


Images courtesy of Bonnie Rasmussen, Oregon Dept. of Agriculture
 
If images are downloaded and used from the ODA web site please be sure to credit the photographer
 
Description
Biennial; blooms early summer. Grows 3 to 7 feet tall. Stems erect. Leaves alternate, one per node, petioled and pinnately divided. Flowers are white in compound stemmed umbels, mostly flat on top. Enlarged taproot is the most easily recognizable feature.
 
Impacts
Poison hemlock grows in pastures, streams, and irrigation ditches.  Several deaths of livestock and humans are attributed each year to this species.
 
Known hazards
Juice from the poison hemlock taproot and it's crown are extremely poisonous. An extract of this species was used to execute Socrates in ancient Greece. It has also accidentally poisoned many who have mistaken it for parsley. Poison hemlock is considered to be one of the most poisonous plants in North America, and is often mistaken for water-parsnip or other edible members of this family. Several deaths of livestock and humans are attributed each year to this species.

Introduction
Poison hemlock is a native of Eurasia.
 
Distribution in Oregon
First documented site of this plant is 1919 in Multnomah County.

Biological controls No approved biological control agent is available.